Jamming circuits, or jammers, are devices that generate electromagnetic radiation for the purpose of deliberately disrupting the successful conveyance of information on a communication link. Jamming transmitters can be configured to transmit on frequencies allocated to specific systems with the intended goal of disrupting information services of that system. The Global Positioning System (GPS) is one such system.
GPS tracking has become ubiquitous; it is an efficient means by which up-to-date whereabouts are maintained for, among many other things, vehicles, equipment, and house-arrest prisoners. GPS tracking capability is now incorporated in many devices as standard equipment, the most notable example of such is various models of cellular phones. Indeed, tracking the location of a child's cellular phone has become popular with many parents. This omnipresence of GPS tracking is considered by some to be invasive and jammers have become a popular mechanism by which concerned people can maintain a sense of privacy. However, jammers, by definition, operate in a frequency spectrum for which they are not lawfully authorized and are illegal for at least that reason in many countries including the United States.
GPS jammers are used to more sinister ends as well, such as to hide from justice or to subvert the recovery of stolen property. GPS jammers are used in military domains as well, including on the battlefield where a lost location fix can be life-threatening.
In light of the foregoing discussion, the desirability of highly portable jamming source locators is apparent.